UNIVERSITY  OF  CALIFORNIA  AGRICULTURAL    EXPERIMENT    STATION 

.LEGE    OF    AGRICULTURE 
BERKELEY,   CALIFORNIA 


COLLEGE    OF    AGRICULTURE  benj.  ide  wheeler,  president 

THOMAS    FORSYTH    HUNT,    Dean    and   Director 


CIRCULAR  No.  89 


HOG  CHOLERA  AND  ITS  PREVENTION. 

By  C.  M.  Haring. 

Why  does  not  California  raise  enough  pork  to  supply  her  own  mar- 
kets? There  are  in  the  great  valleys  of  this  State  superior  advantages 
for  swine  raising.  The  abundant  and  suitable  feed  conditions  and  the 
superior  climatic  advantages  should  make  these  sections  important 
hog  raising  centers.  The  rapid  developments  in  alfalfa  planting  dur- 
ing the  last  twenty  years,  combined  with  the  extensive  changes  from 
wheat  to  barley  culture,  should  naturally  be  followed  by  an  increase 
in  the  number  of  swine  raised.  Twenty-five  years  ago  there  were 
more  hogs  in  California  than  there  are  to-day.  According  to  the  census 
and  the  crop  reports  of  the  United  States  Department  of  Agriculture, 
there  were  in  this  State  in  1886  over  1,000,000  head  of  swine.  By  1900 
this  number  fell  off  to  598,336  head,  and  even  now  it  is  about  800,000. 

One  of  the  chief  reasons  why  ranchers  in  California  do  not  engage 
more  extensively  in  swine  raising  is  the  fear  of  loss  from  hog  cholera. 
From  reports  received  at  the  hog  serum  laboratory  it  is  thought  hog 
cholera  killed  50,000  head  of  hogs  in  California  last  year.  They  would 
have  been  worth,  for  pork,  $425,000,  but  taking  into  consideration 
their  increase  in  weight  and  numbers,  and  the  saving  in  feed  and  fer- 
tility which  they  would  have  wrought,  their  death  loss  totaled  over 
$700,000.  In  one  county  alone  the  loss  from  cholera  was  at  least 
$85,000.  In  another  it  was  $130,000.  According  to  reports  recently 
received  at  the  Agricultural  Experiment  Station,  the  disease  now 
exists  in  thirty-three  counties  of  the  State. 

Nature  of  Hog  Cholera,— The  disease  is  caused  by  germs  so  small 
that  they  will  pass  through  filters  that  will  remove  all  visible  bacteria. 
The  most  powerful  microscopes  known  do  not  magnify  sufficiently  to 
enable  these  germs  to  be  seen,  but  their  presence  can  be  proven  in 
numerous  ways.  They  swarm  in  the  blood  and  excrement  of  sick  hogs 
and  remain  alive  in  the  filth  of  infected  hog  pens  for  months.  They 
are  comparatively  resistant  to  disinfectants.  Exposure  for  weeks  to 
1  per  cent  carbolic  acid  solution  fails  to  kill  them,  although  this 
strength  of  the  disinfectant  will  kill  most  bacteria  in  a  few  hours. 

How  Hog  Cholera  is  Spread.— Hogs  usually  contract  the  disease 
through  infected  food  or  water.  The  disease  germs  do  not  spread 
through  the  air,  for  susceptible  hogs  in  pens  only  a  few  yards  from 
hogs  dying  of  the  cholera  will  remain  well,  provided  their  food  or 
water  does  not  become  contaminated. 

(1) 


—  2  ~ 

The  disease  is  spread  from  ranch  to  ranch  in  the  following  ways : 

1.  Through  streams  and  irrigation  ditches  which  have  been  polluted 
with  the  excretions  or  bodies  of  diseased  hogs. 

2.  Through  the  introduction  of  infected  hogs,  by  purchase  or  other- 
wise. Frequently  hogs  may  have  the  disease  in  such  a  chronic  form 
that  they  show  no  suspicious  symptoms,  but  yet  they  may  be  capable 
of  infecting  susceptible  swine. 

3.  Through  the  use  of  infected  feed.  Garbage  from  kitchens  is  often 
a  cause  of  the  disease.  It  is  a  well  known  fact  that  pork  from  cholera 
infected  hogs  frequently  finds  its  way  into  the  markets,  and,  although 
not  injurious  to  man,  the  uncooked  scraps  of  meat  thrown  into  the 
kitchen  garbage  is  a  not  uncommon  cause  of  infection  to  hogs.  There 
is  also  reason  to  believe  that  tankage  from  slaughterhouses  is  some- 
times infected.  Also,  any  hog  feed  that  has  been  shipped  in  infected 
cars  or  wagons,  or  has  come  in  contact  with  infected  shovels  or  other 
implements,  is  dangerous. 

4.  The  disease  may  be  carried  on  the  boots  of  men,  or  by  dogs  and 
other  animals.  Birds  are  also  believed  to  be  responsible  for  the  spread 
of  the  disease.  The  blackbird,  pigeon,  and  similar  birds  may  feed  on 
the  grain  scattered  to  an  infected  band  of  hogs,  and  then  carry  the 
infection  on  their  feet  to  another  ranch.  Buzzards  are  especially  ob- 
jectionable, because  they  actually  feed  on  the  carcasses  of  hogs  dead 
from  cholera,  when  these  have  not  been  properly  disposed  of,  i.  e., 
burned  or  buried.    Thus,  the  disease  may  be  carried  long  distances. 

How  to  Prevent  Hog  Cholera.— If  the  hogs  on  a  ranch  are  healthy 
they  will  not  develop  the  disease  unless  in  some  way  the  virus  is 
brought  in  from  an  infected  place.  It  cannot  develop  spontaneously. 
External  vigilance  is  especially  required  to  prevent  its  introduction 
when  there  are  diseased  hogs  in  the  vicinity.  Hogs  should  not  be  per- 
mitted access  to  any  stream  or  irrigation  ditch.  It  is  advisable  when- 
ever possible  to  supply  them  with  water  from  wells  or  other  uncon- 
taminated  sources.  They  should  be  kept  in  isolated  fields,  as  far  as 
possible,  and  protected  from  the  intrusion  of  men  or  animals.  The 
filthy  conditions  under  which  hogs  are  frequently  forced  to  live,  while 
not  capable  of  developing  the  cholera,  spontaneously  furnish  a  ready 
means  for  spreading  the  disease  when  it  is  introduced.  The  hog  re- 
quires clean  water  just  as  much  as  any  animal  for  proper  growth  and 
development.  Wallows  are  unnecessary  at  any  time,  except,  possibly, 
during  the  extremely  hot  weather  that  prevails  at  certain  times  in 
some  sections,  and  even  then  they  are  of  doubtful  benefit. 

What  to  do  When  Hog  Cholera  Occurs  in  the  Vicinity.— When  an 
epidemic  of  hog  cholera  occurs,  the  only  safe  thing  for  the  hog  owners 
to  do  is  to  immunize  their  hogs  to  the  disease  by  the  use  of  anti  hog- 
cholera  serum  and  virus.  This  is  obtainable  from  the  University  of 
California.  Until  July  1,  1913,  the  Agricultural  Experiment  Station, 
Berkeley,  will  furnish  500  c.  c.  of  serum  free  of  charge  to  hog  owners 
in  sections  where  hog  cholera  exists.     This  is  enough  to  immunize  15 


hogs  weighing  from  50  to  100  pounds,  or  10  hogs  of  twice  that  weight. 
Application  blanks  are  furnished,  by  the  Agricultural  Experiment 
Station,  but  in  case  of  haste  the  form  at  the  end  of  this  circular  can 
be  filled  out  and  sent  by  telegraph  as  a  night  letter.  The  Agricultural 
Experiment  Station,  at  Berkeley,  manufactures  and  sells  the  serum  to 
hog  raisers  at  actual  cost  of  production,  in  accordance  with  an  act  of 
the  legislature. 

There  are  three  methods  of  producing  immunity.  One  is  called  the 
serum  alone  method  and  consists  of  injecting  anti-hog  cholera  serum 
into  the  muscles  of  the  ham  or  shoulder  by  means  of  a  hypodermic 
syringe.  The  second  is  called  the  serum  and  virus  method,  or  serum 
simultaneous  method.  It  consists  of  injecting  both  the  anti-hog- 
cholera  serum  and  a  small  quantity  of  virus  (virulent  hog-cholera-pro- 
ducing blood).  This  virus  is  injected  with  a  separate  syringe  into  the 
opposite  ham  or  shoulder.  The  third  is  called  the  double  method,  and 
consists  of  the  injection  of  the  serum  alone,  followed  in  ten  days  with 
serum  and  virus. 

The  following  table  shows  the  comparative  cost  and  length  of  im- 
munity of  each  of  these  methods : 


Serum  alone. 

Serum  and  virus. 

Length  of  immunity. 

Cost. 

Length  of  immunity. 

Cost. 

Suckling  pigs  2  to  5  weeks  old 

3  to  6  weeks 

3  to  9  weeks 

3  weeks  to  6  months 

3  weeks  to  6  months 

$0.20 
.40 
.60 
.80 

3  to  6  months 

10  to  18  months 

1  to  2  years 

1  to  2  years 

$0.32 

Weaners  50  pounds  in  weight _- 

.64 

Shoats  100  pounds  in  weight 

.80 

Hogs  200  pounds  in  weight 

1.25 

The  cost  of  the  double  method  is  twice  that  of  the  serum  alone,  but  it 
lias  the  advantage  of  absolute  safety  and  permanent  immunity. 

In  case  a  competent  veterinarian  is  available  to  administer  the 
serum,  it  is  usually  advisable  to  use  the  serum  and  virus  method  or  in 
case  of  valuable  stock  the  double  method.  In  case  no  veterinarian  is 
available  the  Agricultural  Experiment  Station  will,  if  possible,  send  a 
man  to  do  the  work  without  charge,  other  than  actual  traveling  expenses, 
provided  there  are  at  least  150  head  of  hogs  to  be  immunized. 

To  December  31,  1912,  the  Agricultural  Experiment  Station  has  pro- 
duced 1,735,677  c.  c.  of  serum  which  has  been  used  on  86,000  head  of 
swine.  Twelve  per  cent  of  this  serum  were  furnished  free,  and  the 
rest  was  furnished  at  actual  cost  of  production,  which  was  2\  cents 
per  c.  c.  until  September  1,  1912.  Since  then  it  has  been  2  cents  per 
c.  c.  The  actual  cost  of  this  to  the  farmers  was  about  $30,000  and  the 
estimated  saving  by  protecting  hogs  from  cholera  amounted  to  over 
$100,000. 


4  — 


The  following  table  shows  the  results,  in  part,  of  the  use  of  the- 
above  serum,  as  shown  by  signed  reports  received  from  hog  owners : 


Number 
of  hogs 

on  place 

at  time 

serum 

was  used. 


26,180 


Number 
of  hogs 
sick  on 
place 
at  time 
serum 
was  used. 


1,970 


Number 

of  hogs 

that  had 

died 

before 

serum 

was  used. 


Total 
number 
of  hogs 
treated. 


Total 
well  hogs 
treated. 


15,92 


14,995 


Total 
sick  hogs 
treated. 


Total 

number 

well  hogs 

saved. 


Per  cent 

of  well 

hogs 

saved. 


Number       Per  cent 

of  sick  J     of  sick 
hogs  hogs 

saved.  !     saved. 


927 


13,46 


91% 


358 


31% 


The  above  figures  are  in  most  cases  from  ranches  infected  with 
cholera  before  the  serum  was  used. 

In  order  to  be  of  the  greatest  value,  hog  raisers  should  not  wait  for 
the  disease  to  become  evident  in  their  herds,  but  the  hogs  on  all 
ranches  in  the  neighborhood  where  the  disease  exists  should  be  im- 
munized. 

In  cases  where  a  night  telegram  is  necessary  in  sending  for  serum,, 
the  following  form  should  be  used : 

Veterinary  Division,  University  of  California,  Berkeley,  Calif.: 
Send  hog  serum  to 


(Insert  name  of  express  office  here.) 

for hogs,  total  weight. 

( Number  of  hogs.) 


(Total  weight  in  pounds.) 


Before  using  serum,  I  agree  to  fill  out,  sign,  and  mail  to  you  the 
application  blanks  furnished  with  serum.    I  am  a  resident  of  California. 


(Signed) 


(Signature  of  owner  of  hogs.) 


